The present invention relates generally to electronic packages employing mechanical fasteners designed to secure circuit card assemblies in a housing, and more particularly, to an improved electronic package having a high thermal performance wedgelock that secures a circuit card assembly and improves the heat transferred from the circuit card assembly to a housing.
Semiconductor reliability is highly affected by the operating temperature at the junction between the die and the substrate. A 10.degree. C. increase in junction temperature can decrease component reliability by up to 50 percent. Increased performance within the heat conductive path will allow electrical components to operate at lower temperatures under the same conditions, thereby improving reliability. For example, many military and commercial applications require semiconductor junction temperatures to be no higher that 100.degree. C. to 110.degree. C.
Enclosures that are designed to remove heat from circuit card assemblies by way of thermal conduction, such as those assemblies containing high power semiconductor devices, are increasingly challenged to remove higher levels of heat. This is because newly developed semiconductor devices typically contain more circuitry and therefore tend to generate higher heat loads, or because components are smaller, thus permitting the circuit cards to contain more components, thereby increasing amount of heat generated per card.
A wedgelock is a mechanical fastener designed to secure a circuit card assembly in a housing by expanding and applying contact pressure between the circuit card assembly and a card guide surface of the housing. A common style of wedgelock used with conductively cooled circuit card assemblies produced by the assignee of the present invention, for example, is made from aluminum and uses a five piece wedge assembly. The wedge assembly is used as a mechanical fastener to secure the circuit card assembly in the housing by expanding the wedges and causing pressure to be applied between a circuit card assembly card guide surface and either a thermal mounting plate, a thermal management layer, or a portion of the housing.
Heat transfer is achieved by the application of contact pressure between the thermal mounting plate and card guide surface. Conventional wedgelocks used by the assignee of the present invention, for example, are not designed to allow heat conduction through the wedgelocks. Estimates show that only three percent of the heat load is conducted through the conventional five piece aluminum wedgelock. This low heat conduction is due to the very small contact area between individual wedges when they are in an expanded condition to secure the circuit card assembly.
Accordingly, it is an objective of the present invention to provide for an improved electronic package and high thermal performance wedgelocks that secure a circuit card assembly in the package and improve the heat transferred from the circuit card assembly to a housing of the package.